1. Technical Field
The present invention relates to a sheet manufacturing apparatus and a method for manufacturing a sheet.
2. Related Art
In sheet manufacturing apparatuses, a so-called wet format has been employed, where a stock material comprising fiber is poured into water, defibration is performed primarily by a mechanical action, and defibrated material are spread and dried to make a sheet again. A sheet manufacturing apparatus of such a wet form requires large amounts of water, and the apparatus is quite large. In addition, considerable time is spent in the maintenance of keeping water treatment facilities in good condition, and the process of drying also takes a large amount of energy.
Sheet manufacturing apparatuses using a dry approach, where water is not utilized to the greatest extent possible, have therefore been proposed in order to reduce scale and conserve energy (see, for example, Japanese laid-open patent publication No. 2012-144819).
Japanese laid-open patent publication No. 2012-144819 discloses defibrating a piece of paper into fibers in a dry defibrating machine, deinking the fibers in a cyclone, passing the deinked fibers through a small-hole screen of a forming drum surface and depositing same onto a mesh belt, to form paper.
When the piece of paper is defibrated in a dry defibrating machine such as is described above, then in some instances a defibrated material having a variety of fiber lengths is produced. When, for example, a defibrated material of short fiber length is admixed into a material for manufacturing paper, then in some instances binding with the other fibers is more difficult, the binding strength of the defibrated material is decreased, and the strength of the paper thus manufactured is decreased.
Also, in some instances it is impossible to completely defibrate the pieces of paper in the dry defibration machine. When undefibrated pieces that have not been defibrated into fibers are admixed into the material for manufacturing the paper, then sometimes the texture of the paper thus manufactured is deteriorated. Sometimes, also, such undefibrated pieces bind less readily with the other fibers and therefore the strength of the paper thus manufactured is decreased.